Dear Papa

Dear Papa,
I have recently discovered a confusing truth.
One I cannot simply brush aside.
Forgive me, dear Papa, I wish to be good,
for a good girl you have taught me to be.
You see,
I came across a collection of letters,
Old-fashioned, 2D letters;
In one I found dear Mama's writing,
In another dear Uncle's answer.
Now my question is, dear Papa;
Where do you come in?